This invention relates to a process for removing residual material from plastic containers such as those used for motor oils, detergents and other liquid products. The plastic containers are cleaned so that the plastic can be recycled for making new plastic products. The residual material such as motor oil is reclaimed and can also be recycled.
Numerous reclamation processed have been developed for specific types of plastics containers used for different materials. Previous processes require reduction of the plastic containers to small particles which requires heavy duty grinding equipment that can handle the residue and trash often associated with reclaimed plastic containers and which results in excessive wear on the grinders and other process equipment from both the small plastic particles and from the residual trash which often includes sand, dirt and other abrasive material. The small plastic particles themselves are typically abrasive and are frequently processed by attrition, by using high energy centrifugal equipment and frequently using powerful and toxic hydrocarbon or organic based solvents. Each of these requirements results in an expensive process in terms of complex equipment costs, operating costs, material costs and excessive wear on the equipment. Typical processes are described in the following patents:
U.S. Pat. No. 4,606,774 to Morris describes a process for removing contaminates from soil by washing the soil with a counter-current stream of a hydrocarbon solvent as the soil passes through an incline screw. Solvent entrained in the soil is removed by a hot air stream in a fluidized bed scrubber and the recovered solvent is purified by a distillation process.
U.S. Pat. No. 4,906,302 to Bruya describes a process for removing organic hazardous waste from soil using an aqueous ammonia solvent. The soil is removed, crushed, screened, agitated with the ammonia solvent and separated from the solvent in settling tanks. The solvent is then purified by a centrifuge, then extraction and distillation.
U.S. Pat. No. 4,956,033 to Martin et. al. describes a process for reclaiming plastic containers by sorting the containers by capacity of the bottle and type of plastic, then removing caps and retaining rings. Each bottle is then expanded by injecting heated liquid internally, then washing the container with a high pressure spray and finally grinding the container. Water can be the liquid used for expansion and washing. The expansion step removes labels and adhesive from the bottle.
U.S. Pat. No. 5,084,135 to Brooks et. al. describes a process for recovering cellulose fiber from partially processed cardboard having some plastic coating material associated with it by repulping the cellulose and plastic material in an aqueous bath in which the plastic tends to float and the cellulose tends to sink. The cellulose and plastic are dried and recycled.
U.S. Pat. No. 5,160,441 to Lundquist describes a process for separating motor oil from granulated plastic particles using a continuous fed auger-centrifuge. The residual oil is recovered in concentrated form although an optional solvent wash is also described.
U.S. Pat. No. 5,185,041 to Anderson et. al. describes a process for washing plastic granules using a rotating drum housing containing a wash solvent header and a rinse header to wash and rinse the plastic granules in sequence. The washed granules are spin dried for recycling.
U.S. Pat. No. 5,215,596 to Slyke describes a process for washing drill cuttings from a mine or oil well drilling operation which uses an oil-based drilling mud in which the cuttings are treated with a high carbon carboxylic acid then washed with an aqueous, alkaline solution.
U.S. Pat. No. 5,217,628 to Lundquist describes a process for centrifugally separating motor oil from granulated plastic particles using a high centrifugal energy batch type apparatus without any solvent.
U.S. Pat. No. 5,232,607 to Lundquist describes a process for granulating plastic containers then separating motor oil from the plastic granules using a high centrifugal energy batch type apparatus without any solvent.
U.S. Pat. No. 5,236,603 to Sampson describes a process for reclaiming plastic from mild jugs by granulating the plastic containers the using a cold water wash step to remove bacterial and residual milk products then separating the plastic granules according to specific gravity using one or a series of aqueous solvent baths each having a different specific gravity.
U.S. Pat. No. 5,255,859 to Peacock et. al. describes a process for separating plastic flakes from foreign matter by first classifying the plastic flakes and other material the washing and digesting the plastic flakes or granules in a recirculating tank for a sufficient time to separate the plastic flakes and foreign matter. The plastic flakes are then screened and dried for recycling.